In the fields of pharmaceuticals and pesticides, many methods for microencapsulating a biologically active substance have conventionally been tried in order to enhance potency, reduce toxicity and impart stability (see, e.g., WO 95/13698 and JP-A-2004-196718). In the printing and the paper industries, microencapsulation of pigment and dye has already been put in practical use.
For example, there are some known methods for microencapsulating a solid biologically active substance. Microencapsulation by interfacial polymerization generally requires a solid substance to be dissolved in a specific solvent, and must be designed to produce a suitable formulation for the solid substance according to properties of the solid substance, for example, by selecting an appropriate solvent. Microencapsulation by spray-drying produces a microcapsule having low wall denseness to be difficult to achieve well controlled-release, and often produce some aggregates at the time of the production. The method thus has a problem of difficulty in particle design. Microencapsulation by orifice method or the like has a limitation in production method, and is difficult to produce a microcapsule having small particle size. A microcapsule produced by the method also has a problem that in some cases of use as an aqueous suspension, suspension stability cannot be maintained. Microencapsulation by meltable dispersion process has a limitation of a melting point of a coating material that can be used and a problem of a limited feature of the resultant microcapsule.